Winding for alternating-current apparatus



Se t. -1 2 p 9 7 M. A. SAVAGE WINDING FOR ALTERNATING CURRENT APPARATUSFiled Dec; 29} 1925 Invensor: Morion A.Sqvage, by His Attor'neg.

Patented Sept. 20, 1927. I

. UNITEDTSTATES 1,643,178 ara-NT OFFICE.

rumor a. savaen, or scorn, Rnwronx, 'asslerton 'ro GENERAL. nmcc'rm'coourm, a COZBPOBATIQN or raw roux.

WINDING FOB ALTEBNATING-CUWT Application filed De'cembei' 29, 1025.Serial m. 78,209.

My invention relates to electrical apparatus, and more particularly tothe windings of alternating current apparatus.

11 large alternating current generators in l which the windings, whichare disposed in a the armature slots, consist of conductors ofconsiderable depth, the ma etic flux-across the slots due-to the current1n the conductors 'ves rise to parasitic voltages in the con- 1 uctorswhich induce eddy currents therein. These currents if'of suflicientmagnitude ma produce objectionable heating of" v the win ing and causethe material of the conductor to be inefliciently utilized.

In such a machine, where each armature slot is filled with severalconductors arranged one above the other, the flux due to current carriedb the bottom conductor has a path partly t rough the iron core andpartly through the space between the side walls of the slot. Thedistribution of this .flux for convenience may be regarded as uni-' formfrom the top of the conductor to the mouth of the slot. Likewise theflux due 95 to current carried by the second conductor from the bottomalso may be regarded as evenly distributed in the space between the slotwalls from the top'of that conductor to the mouth of the slot andsimilarly for 80 the remaining OODdllCtOlS'lD. the slot. The total fluxdensity in the slot therefore is not uniform'but increases from the topof the bottom conductor to the mouth of the slot. In the above,consideration has beengiven only to the flux'between the top of aconductor and the mouth of-the slot. Current in each conductor producesa flux throu hout the depth of t e conductor which ux increases from thebottom to the top of the conductor and produces a voltage in theconductor which increases from the bottom of .the conductor to the topthereof in ap roximately a parabolic manner. The tota voltage in-anyhalf turn of a coil is thus made up of a voltage due to the flux of thathalf turn of the coil lus the voltage due to the flux from the ot erhalf turnsof the coil below the one in question. This voltage variesinmagnitude for each half turn, be-

ing greatest for that half turn at the top of the slot. The voltagesinduced in the two sides of the coil are in opposite senses due to thefact that the reversing end turn of the winding inverts one side of thecoil"- relativeto the other side. As a result of this reversal the.difierence of vo'lta es induced in the topandfthe bottom portions ofthe conductor in one side of the coil-is partly neutralized by thatin'the other side of the coil. But, because of the unequal distribu tlono f flux throughout the depth of the slot as pointed out above therestill remains a voltage difi'er'ence between the top and the bottomportions of the 'conductor which gives rise. to objectionable eddycurrents through the conductor forming the winding.

As a means of reducing these eddy current losses it has been proposed touses. stranded conductor and to twist the part of the-conductor whichlies in the slot to vary the relative position of the various strands.Such a winding has the serious objections of lncreased cost ofmanufacture due to the use of special tools and greater labor as well asto the necessity of greater slot depth.

It has also been proposed to divide the strands of eachconductor intotwo or more groups and, to carr these separate groups through several00' s with proper transposition before finally clip ing them altogether.This method has t e objection of requirlng' fairly com licated cross.connwtions atthe c ips an of giving'a considerabiy high voltage betweenstrands t is an object of my inve'ntionto provide an improved windingwherein the eddy current losses are reduced to a relativel low value bygiving to the strandedcdn uctor forming the windin twists arranged inthe-' portions of the win ing which lie outside of and Qwhich connectthe portions thereof which lie in the slots} In the specific form of myinvention illustrated, I form the a winding of coils constructed in thecustom-- ary manner and having the usual terminal connections and inthese terminal connections I give the conductor a twist of substantiallydegrees; Each two adjacent coils joined by suchterminal connections.thus will have the eddy currents of one coil 0 posing the eddy currentsof the other. i ince. the coils areopposed to each other in pairs theconductor may be twisted in only alternate terminal connections, theremain- .ing terminal connections having the usual form.-

My invention will be better understood from the following descriptiontaken 001. i

- voltage is so' low that the rnxrig; 4,-1 have shown coil terminals 15;

'gndnoogun them.

nection with the accompanying drawing, and its scope will be pointed outin the appended clalms. p In the drawing, Fig. 1 shows two adjacentcoils of a winding with terminal connections illustrating one embodimentof my invention; Fig. 2 1s a cross section of the coils of Fig. 1 online 22 showing them -in their respective core slots; Fig. 3 is a detailof the type of terminal connection shown in Fig. 1; and Figs. 4 and 5are similar details of modified forms of terminal connections embodyingmy invention.

The two coils 1 and 2 of Figs. 1 and 2 are shown as three-turn coils,the left hand sides of coils 1 and 2 occupying the bottoms of slots 3and 4 respectively and the right hand sides of'these coils occupying thetops of slots 5 and 6 res ctively. In Figs. 1'

and 3 I have shown t e upper terminal lead 7 of each coil twistedthrough 180 and connected to the lower terminallead 9 of the next coilby an insulating clip .10. The conductor forming the coils is shown ascom-' four individually insulated double.

prism stran s and the clip 10 as comprising four separate insulatedconnectors 11 which serve to electrically connect the double strands inpairs as shown while maintaining the respective strands insulated fromeach other.

In order that the efi'ect of the twist 8 may be. more readily seen Ihave shown one double strand shaded throughout the two coils. Thus inslot 3 the shaded strand of coil 1 is at the bottom of the conductor andin slot 5 the shaded strand is at thetop of the conductor due to theefiect of the rear reversing end turn 12. In slot 4 the shaded strandagain is at the top because the conthe front reversing end turn 13 andthe other at the twist 8. The shaded strand'in slot 6 is again oppositeto that in slot 4 due to the rear reve end turn 14. It

will be seen therefore that the" voltage difference induced in thestrands of one coil tending to cause eddy currents to circulate g havingfor reduc" '1 therein comprising twlsts of substantherein is neutralizedby a equal and oppo: site voltage difierenceanduced in the next ad'acentcoil.

ue, however,- to the small difference in ..'time phase of the parasiticvoltages in two coils when these coils share their slots with coils ofdifferent phases the eddy currents may not be reduced to zero, but insuch a case the reduction is material and the resultare l andflfl-correspond n totermina-ls 7 and}? each by the single 180 twist shown inand 4.

a simple and non expensive means of ductor has undergone two reversals,one at.-

and other portions connecting said portions,

7 a;90 twlstat points 17 and 18 y by wh ch e same object isac'comphsiied as ig. 3'.

tween the coils at the clIip and such an arrangement is shown in 1g. 5.Here as in Fi 3 and 4, the strands are insulated from eac other at theclip, butto simplify the drawing no insulation has been shown. By theconnectors 19 and 20, the to and bot: tom strands of one coil termindlare connected to the respective top and bottom strands of another coilterminal, thus securing the same effect as those connections shown inFigs. 3 and 4. In generalthe middle two or three strands -may be solidlyclipped together, as'shown at 21, without causing much additional loss,and such an arrangement is resorted to in Fig. 5 to simplify the clipstructure. It is to be understood that this same expedient may be usedin connections such as. shown in Figs. 3

Since the coils are balanced against each other in pairs each alternateconnecting clip may, if desired, be made solid in which case the strandsare not insulated from each other but all electrically connectedtogether. In practice, however, the existence of odd numbers of slots insome phase belts, the desirability of keeping the pole connection clipssolid, and of preserving uniformity in all the coils results in the useof the special method of clippin filin all the'connections between thecoils. '5 gives alarge factor of. safety since every other clip can beshort circuited; without increasing the losses.

It will thus be seen that haveprovided' ac comphshing the dem'red resultof eliminating eddy current losses in coil windin Also by my method Iavoid excessive vofi llg b6- tween strands and all the advantagesincident to the use of formwound. coils.

What I claim, as new and desire to secure by Letters Patent of theUnited States, is:

.1. A for 'alterna current ap'-' paratus comprising slot-em ded portionssaid windings, being formed of a conductor having a plurality ofinsulated strands and eddy current tially.1.80 d in the conductorarranged in saidconnectin portions. 2. A or alternating current a aratuscomprisi a: plura ity of 005; ormed of Va eon uctor having insulatedattends, the top and bottom'strands of one coil-terminal being connectedinseries with the. 'vetop and bottom strands of from .a l-. Y'acmt-atranlfiwherebgthevoltage difieren'c'e "of the conductor of coilisv substantially neutraIi'zed-byfthe. in the-strandsofvoltagediflerence A thgctxiductor inthe other coil. 1. p f

- winding. comp a.p urah o coils formed of. con uctor of strandsinsulated throughout the coil, and means for connecting and insulatinstrands of one coil in series with strands 0 another coil which arereversed in order relative to the axis of the conductor. v

4. A winding comprising a plurality of coils having reversing end turnsand formed of conductors comprising insulated strands, and meansconnecting the strands of one coil terminal with the respective strandsof another coil terminal while maintaining the respective strandsinsulated from each other,

said means including conductors in the form of a loop in which the orderof the strands is reversed, the conductor comprising said loop beingtwisted substantially. 180 degrees.

5. A winding for a dynamo-electric machine comprising a lurality ofcoils each having reversing end turns and formed of conductorscomprising a plurality of insulated strands, and means comprisinginsulated connectors for connecting the strands v of the terminal of onecoil in series with the respective strands of the terminal of anothercoil, said connected terminals formin a reversing loop'and one of saidtermina hav--- ing a twist of substantially 180 degrees therein.

6. A winding for dynamo-electric machines comprising a pair of adjacentcoils, each havin a reversing end turn at each end thereof an beingformed of conductors comprising a plurality of insulated strands, and aconnecting clip comprising separate insulated connectors for connectingthe strands of the terminal of one coil in series with the respectivestrands of the terminal of the adjacent coil, said connected terminalsforming a reversing loop and one of said terminals having a twisttherein of substantially 180 degrees.

In witness whereof, I have hereunto set my hand this 24th da ofDecember, 1925.

' MARiON A. SAVAGE.

